Method of forming heat transfer units



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METHOD 0E EORMING HEAT TRANSFER UNITS Filed June 14, 1956 4 Sheets-Sheet 2 Aug. l, 1961 R. w. KRlTzER 2,994,123

METHOD OF FORMING HEAT TRANSFER UNITS Filed June 14, 1956 4 Sheets-Sheet 3 www CZ @o T22@ ug. 1, T961 Filed June 14, 1956 R. W. KRITZER METHOD OF FORMING HEAT TRANSFER UNITS 4 Sheets-Sheet 3 A Qs entre..

The invention relates to heat transfer units which include ltubing and fins and to the fabrication thereof.

One object of the invention is to provide a fin-structure which is adapted for use with a variable number of tubing sections, iins of varying length to extend over areas of variable dimensions, for heat-transfer units of different capacities.

Another object of the invention is to provide an irnproved method of fabricating a iin-structure which is adapted for uses with djiferent numbers of tubing sections and to provide finned areas on the tubing of varying dimensions.

Other objects will appear from the detailed description.

The invention consists in the several novel features which are hereinafter set forth and more particularly defined by the claim at the conclusion hereof.

In the drawings:

FIG. 1 is a plan view of a continuous web of lin-stock which has been fabricated Iwith openings for the tubingsections surrounded by annular anges, ribs producing turbulence and perforations, through which air can pass, preparatory to severing the web longitudinally into iinstr'ips for` assembly with tubing;

FIG. 2 is a section taken on line 2 2 of FIG. l on a larger scale;

FIG. 3 is a section taken on line 3 3 of FIG. l also on a larger scale;

FIG. 4 is a section taken on line 4 4 of FIG. 1 also on a larger scale;

FIG. 5 is a longitudinal section of lone of the lin-strips bent into serially `connected sections preparatory to its assembly with tubing;

FIG. 6 is a plan View of an assembled heat transfer unit;

FIG. 7 is a partial side elevation of the assembled unit, the tubing being shown in section;

7 FIG. 8 is a partial section taken on line 8 8 of FIG. FIG. 8a is a section taken on line 8a 8a of FIG. 8; FIG. 9 is a plan View of the stationary bed of a press and tools mounted thereon used for forming the openings for the tubing, annular flanges around said openings and 'the ribs on the web, the guides for the reciprocable head being shown in section;

FIG. 9a is a section taken on line 9a-9a of FIG. 9;

FIG. 10 is a vertical longitudinal section of the coacting tools on the stationary bed and the reciprocable head of the press, taken on line 10 10 of FIG. 9;

FIG. ll is a section illustrating the tools for forming bulges on the web of iin-stock;

FIG. 12 is a section illustrating the tools for piercing or rupturing the bulges formed on the web preparatory rto shaping them into annular flanges;

FIG. 13 is a section illustrating the dies for accurately shaping the annular flanges aro-und the openings `for the tubing; and

FIG. 14 is a section illustrating one of the stripperplungers.

' The invention utilizes an elongated or continuous web of fin-stock which is supplied from a coil of great length on a reel, and ywhich is severable into elongated strips which are bendable transversely to forni serially connected iin-sections. Series of longitudinally spaced openings, each surrounded by an annular flange, are formed in longitudinal zones ofthe web of iin-stock and the longi tudinal zones are severed from one another by longitudinal `cuts to provide elongated strips. The iin-stock is transversely bendable to form series of tin-sections of varying lengths according to the desired number of tubing-sections and the desired area thereof to be provided with tins. 'This adapts like strips of fin-stock to be utilized in the fabrication of heat transfer units which include tubing-coil sections of varying nrunbers and finned areas of varying dimensions. Like fabricated stock is available for the expeditious fabrication of units with different numbers and dimensions of coil-sections and variable finned areas. This results in economy in the cost and expedites the production of assembled units of different commercial specifications.

In the fabrication of the units, a web of suitable finstock 20 is usually fed from a supply reel. The web may be of any suitable width and may be of sheet aluminum of .006 in thickness which is exible and highly eiiicient in heat conduction. symmetrical longitudinally spaced series of openings 21 for receiving tubing-sections 22 are formed in symmetrically and transversely spaced series across the web. Each opening 21 is surrounded by an annular flange 23 projecting from one face of the web. The alternate ilanges in each longitudinal series extend from opposite faces of the web, as shown in FIG. 2. At each side of each yopening 21 and ange 23 the web 20 has embossed ribs 24 for producing turbulence in the air iiow between iin-sections in the assembled units. The ribs 24 at the sides of alternate openings 21 in each longitudinal series, project from the opposite faces of the web. Perforations 25 are formed in the web 20 between the longitudinally adjacent openings 21 to permit some air to -flow through iin-sections. The annular flanges 23 provide increased contact area between the tubing and the iinsections and also function to space the sections apart in the assembled units. After the web has been provided with the longitudinal series of openings 2l, ilanges 23 ribs 24 and perforations 25, it is severed longitudinally along dotted lines 26 to form elongated iin-strips 27 of :great length, each strip having a longitudinally and symmetrically spaced series of openings 21 adapted to receive a section of tubing of a predetermined diameter, anges 23 surrounding the openings 21 and alternately projecting from opposite faces of the web, ribs 24 projecting from the opposite faces of theweb at the sides of alternate openings 2\1 and perforations 2S in the web between said openings. In this manner there yis produced from the web, a multiple or series of strips 27 of the desired width, in any desired length, and bendable as at 29, into a iin-structure. These strips are bendable transversely at different points, preferably across perforations 25 to provide iin-sections of 'varying length, or for units of different dimensions or varying numbers of tubing-sections. ln this manner, a stock can be maintained of strips for the fabrication and assembly of units of different dimensions or capacity and `different numbers of tubing sections.

In assembling the heat transfer units, a strip 27 with the openings 21, anges 23 and ribs 24, is bent as at 29 transversely and severed from the web approximately into the contour shown in FIG. 5 to form fin-sections 27a each with the number of openings 21 and anges 23 corresponding to the number of tubing-sections to be included in the unit and in length corresponding to the number of sections desired in the finned area of the unit. A sufficient number of these sections are bent to provide a number of ns for the desired width of the finned area of the unit, and for continuity are serially connected by bends alternately between opposite ends of contiguous sections. Tubing sections 30 slightly less in diameter than the openings 21 are then inserted serially through said openings and the sections 27a are forced together until they are substantially parallel between the bends 29, and the openings 23 in the sections will be aligned so that tubing-sections 30 for the entire unit can be inserted through nasections as shown in FIG. 6, with the flanges 23 spacing said sec-tions apart for the flow of air. Next, the tubing-sections are expanded by forcing a suitable mandrel through the tubing-sections or by internal fluid pressure, for forcing the outer periphery of the tubing into pressure-contact with the inner peripheries of said flanges and for etiicient heat conduction. Connecting bends 31 are then serially connected to the ends of the tubing sections to form a coil for the flow of refrigerant therethrough while the iinstructure conducts heat to the ambient atmosphere. The unit will then be completely assembled for use.

The openings 2l, flanges 23 and ribs 24, in multiple, are formed in the web for their simultaneous formation in transverse zones of a set of said openings, flanges and ribs, and consecutively in the longitudinal Zones which are severed into strips 27 by suitable tools in a power press which includes a stationary bed a and reciprocable head b which is operable by any suitable power driven mechanism. Multiple sets of tools are provided, one for each longitudinal zone of the web which is subsequently severed into strips 27 and are disposed in side-byside relation in the press. Each set of tools is adapted to form consecutively along one of said zones, a pair of openings 2l with surrounding flanges 23, associated ribs 24, and perforations 25, during successive operations of the press and` step-by-step advances of the web. Each of said sets of tools includes tools mounted on the bed a and mating or coacting tools mounted on the head b. Collectively, the multiple sets of tools form the openings 21, anges 23 and ribs 24 in the entire series of longitudinal strip-forming zo-nes of the web. The tools of each set are of like construction, respectively. The tools on the bed a are mounted on a pair of plates a1 and a2 which are demount-ably secured on said bed and the coacting tools on head b are demountably secured on plates b1 and b2 which are movable with said head, for convenience in assembly and replacement of said tools. The plates a1 and a2 function as a part of the bed or stationary member of the press and the plates b1 and b2 function as a part of the head or movable member of the press.

Each set of tools for forming the annular flanges 23, includes a deforming tool 35 which is secured in plates a1 and a2 on bed a and a coacting socket 36 in plate b1 which are adapted to form an upward bulge 37 on the web 20 and a tool 38 which is secured in plates b1 and b2 on head b and coacts with a socket 39 in plate a1 for forming a downward bulge or deformation 44] on the web 20 in longitudinal alignment with bulge 37, during each operation of the press, `as shown in FIG. ll. The entire web will next be vadvanced one step to position the bulges 37 between a deforming tool 4Z on head b and a socket 43 on plate al on bed a and to position bulge 40 between a tool 44 in plates a1 and a2 and a spring-pressed slidable plunger 45 in plate b1 and b3. When the web is thus advanced and head b is again operated, the bulge 37 will be deformed or stretched into a pierced bulge 47 and bulge 40 will be simultaneously re-shaped as shown at 48 in FIG. l2. The web 20 is next advanced longitudinally to vertically align bulge 47 with a punch 49 in plate b1 and a socket 50 in plates a1 and a2 and to simultaneously align bulge 4S with a punch 51 in plates b1 and b2 of head b and a socket 52 in plates a1 and a2 as shown in FIG. 10. When the press is again operated the punches 49 and 51 will cut disks from the previously deformed portions 47 and 48 and discharge them through the downwardly ared openings in sockets 50 and 52 in plates a1 and a2 and bed a, flanges will be formed to surround the openings 21 and project from opposite faces of the web. The

il web is next advanced to axially align one flange 23 with a female die 55 in plates a1 and a2 and a male die 56 in plates b1 and b2 and to axially align the other flange with a male die 57 in plates a1 and a2 and a female die 53 in plates bl and b2, During the next stroke of the head b of the press, these dies will produce uniform annular flanges 23 projecting from opposite faces of the web between the dies 59 and 56 and dies 57 and 58, respectively, as shown in FIG. 13 for accurate surrounding correlation with tubing extending through the openings 21. Perforations 25 are punched in the web by a pair of punches 62 which are mounted in plates b1 and b2 and a mating pair of female dies 63 which are mounted in plates al and a2.

Each set 0f tools on the press includes a pair of dies 70 (FIGS. 9 and 9a) confined in plate al, each of which has a rib 71 and a longitudinally aligned recess 72 which coacts with a pair of dies 74 in plate b1, each of which has a recess 76 coacting with rib 7l and a rib 75 coacting with recess 72 to bend pairs of ribs 24 in the sheet 20 at the sides of each flange 23 when said flanges are being shaped between dies 55 and 56, and 57 and 58, the ribs projecting alternately from opposite faces of the sheet 20.

Successive strokes of the press operate these tools to to pro-duce a web with longitudinal series of longitudinally spaced openings 23 surrounded by annular flanges 23 projecting alternately from opposite faces of the web, ribs 24 projecting alternately from opposite faces of the web, and perforations 25 between openings 21. The web is produced with multiple transverse series of these formations so that the web when severed along the lines 26 will provide strips of lin-stock which is bendable transversely into strips 27 for use in assembling a continuous strip of fin-structure with the tubing to complete the units.

Series of plungers 68 are vertically slidable in plates a1 and a2 and their upper ends are adapted to support the web 20 of lin-stock between the tools in position to be operated upon by the press. Each plunger is slidably mounted in plates a1 and a2 and has a shoulder 61 for limiting its upward movement by a spring 69 which is confined in plates a1 and a2 of the bed. The plungers 63 are provided at the points necessary for initially supporting the web 2t) above the tools on bed a. Springs 69 permit the web to be .forced down to plate a1 during each down stroke of head b and force said web after each operation to release or strip the web from the tools for successive steps of advance and successive operations of the tools on consecutive portions of the web.

When the web has been severed on lines 26 to form strips 27, the latter may be bent on transverse lines to produce strip-sections of different lengths and for different numbers of tubing-sections, land with finned areas of any desired widths so that fabricated strips Will be available for expeditiously and economically assembling fabricated strips 27 and tubing-sections for heat transfer units of diiferent dimensions. For example, the strips may be bent to provide serially connected sections 27a with openings 2l and flanges 23 for a unit with six or any other desired number of tubing sections or sections for finned areas of different widths or lengths of the tubing sections. The fabricated strips are also usable on tubing which is circular or spiral in contour because of the dexibility of the strip.

The invention is not to be understood as restricted to the details set forth since these may be modified Within the scope of the appended claim without departing from the spirit and scope of the invention.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is:

The method of fabricating finned heat transfer tubing from a flat strip of sheet metal stock and cylindrical tube stock which comprises: establishing a series of equally spaced parallel fold lines transversely of the strip and medially of the ends thereof, forming in said strip a small perforation at each established fold line, forming in said strip between each adjacent pair of fold lines a row of spaced circular tube openings surrounded by annular flanges which project out of the plane of the stock with said rows extending in alignment, the spacing ofthe openings on opposite sides of each fold line being identical so that when the strip is folded on said fold line the openings will be brought into approximate axial alignment in pairs, the annular flanges which are equally spaced from each fold line extending in opposite directions, folding said strip on said fold lines alternately in opposite directions to thus bring said openings into such approximate alignment With the anges of the approximately aligned openings extending in the same general direction and to thus create oppositely facing notches Iat alternate fold lines respectively, inserting ya length of cylindrical tube stock through each series of approximately aligned openings and, nally, expanding the tube stock lengths into intimate face-to-face frictional contact with the inside surfaces of the flanges through which they project.

References Cited in the file of this patent UNITED STATES PATENTS Commichau Sept. 30, 1902 Henshall Feb. 26, 1929 Kalloch Jan. 6, 1931 Swanstrom Feb. 12, 1935 Hardiman Dec. 8, 1936 Schank et al Aug. 12, 1941 Kramer Alug. 19, 1947 Askine Sept. 16, 1947 Kramer July 5, 1949 Echols Oct. 4, A1949 Kritzer Feb. 6, 1951 Greer Sept. 6, 1955 Hayward Sept. 4, 1956 FOREIGN PATENTS France May 25, 1918 France Ian. 4, 1938 France Jan. 22, 1942 

